This invention relates to measurement devices, in particular, a vehicle for measuring the geometric condition of a railway track in relation to the theoretical geometric configuration of the said track.
There are various procedures and means of measuring in which the discrepancies in position of one point in the track with respect to its theoretical line are detected by appropriate devices commonly called bases of reference. These devices are often supported on the track and help establish the desired line. These procedures may come within two main categories. namely (1) bases of reference called absolute references, which allow the successive positions of a mobile point to be determined as it covers the track in relation to a fixed reference, and (2) so-called relative bases of reference, which allow the successive positions of a point travelling along the track to be determined in a manner that is no longer defined, in this case, not in relation to a fixed reference, but in relation to a mobile reference defined by a sufficient number of points held at constant distances from each other which are stationed along the length of the track.
This invention falls within the latter category, namely the proposal is for a measuring vehicle whose chassis constitutes the so-called relative reference base. The measurements in relation to this relative base may be taken in different ways which are not this subject of this invention, but two more recent devices will be discussed, namely the use of three measuring undercarriages interdependent of this base of reference (which is the chassis) and, the second by means of a so-called inertial platform and two measuring undercarriages which allow measurement of deviation, in a vertical plane and in a horizontal plane, between the two corresponding measuring points on the two measuring undercarriages.
The fact that trains, and passenger trains in particular, are running at ever greater speeds makes it indispensable to have track measurements which can detect waved deformations of the track, whether these have a small or a large wave length. When using a fixed base, which is the vehicle chassis, the quality of the measurement is linked to the rigidity of the chassis. Nevertheless it is obvious that a chassis some ten meters long cannot easily be considered to be absolutely rigid, short of providing an extremely heavy structure. In order to detect, with any accuracy, the waves of deformation showing a large wave length, vehicles have to be built with even longer chassis, something in the order of twenty meters, and then it is virtually impossible to build them without an extremely heavy rigid chassis structure, i.e. (vehicles) that is not subject to any elastic deformation while travelling on a railway track. Since the measurements are taken with respect to the chassis of the mechanism, it is clear that any possible deformation of the chassis may influence the results of the measurement by respectively increasing or decreasing the actual values.
A vehicle is provided for measuring the geometric condition of a railway track in relation to the theoretical geometric configuration of the said track. The vehicle includes a rigid chassis forming the measuring base. The chassis is supported by the means of rolling on the railway track. The vehicle includes a probing device that finds the geometric configuration of the track and the degradation of the geometric configuration in relation to the theoretical geometric configuration and to show any possible discrepancies representing the said degradation.
The aim of this invention is to provide a measuring vehicle whose base is constituted of the chassis of the said vehicle, allowing the influence of deformation of the said chassis to be eliminated, particularly when it is an especially long chassis.
The vehicle according to the invention is characterised by the fact that the chassis is furnished with opto-electronic means laid out to measure the elastic deformations of the chassis whilst travelling on the said vehicle track, the said deformation values of the chassis being supplied to the means of probing to correct the values of the geometric configuration found.
The advantage of the vehicle according to this invention is the fact that any possible deformations of the chassis due to irregularities in the track, and also due to deformation inherent in the size of the chassis, are measured and supplied to the means of probing to facilitate the correction of the measurements taken with respect to the chassis.
According to a first preferred embodiment of the invention, the opto-electronic means include an optical receiver device made up of sensors, each provided with several photosensitive elements for receiving light beams emitted by light sources located at a distance from the receiver measuring device on either side of the latter, two systems of lenses arranged in the zone situated between the light sources on both sides of the receiver device, each light source being linked to at least one of the sensors receiving the lights beams emitted by the corresponding light source and crossing the corresponding system of lenses, the two lens systems being made up of a fixed lens, whose optical axes are aligned and where the photo-sensitive elements of each sensor are aligned in such as way that the light rays passing through the lens in question are projected, as a function of their angle of incidence, onto a corresponding zone of the sensor, with the device and the light sources being interdependent on the said chassis. The opto-electronic means are those described in the U.S. Pat. No. 5,255,066 (the content of which is incorporated by reference) of the instant applicant, a device which was originally provided for measuring deformation in railway tracks. These means are now used to measure only the deformation of the chassis and are set out in a permanent arrangement, namely with the light sources at either end of the chassis, whilst the optical receiver is towards the middle of the chassis.
According to the first embodiment for carrying out the invention, the device for taking the bearings of the track comprises three undercarriage devices probing the railway track, allowing the geometric co-ordinates of the track to be taken at three points in relation to the chassis (9) in the plane of the line and in the plane of the profile. These devices are, in principle, vertically alligned, with, on the one hand, the light sources and, on the other hand, the receiver device. These devices measure the position of three points in relation to die chassis, the said position being corrected by any possible deformation of the chassis found by the opto-electronic device. Therefore, the actual position of these three points is known. The sensors are either mechanical devices (wheels), electronic, or optical.
According to the first embodiment for invention, the vehicle is provided with two undercarriages for probing the track to find the geometric position of the track at two points in relation to the chassis, and an absolute three-dimensional so-called inertial reference platform, the said platform being laid out to measure the vectoral difference between the chassis and North and between the chassis and the horizontal plane, thus allowing the curves of the track to be determined in the horizontal and vertical plane, and also the vertical slant.
The said inertial platform is provided in three planes with accelerometers, gyroscopes and means for processing signals, in order to determine special line defects.
The said platform is connected to a point on the chassis, preferably a point common to the chassis and one of the undercarriage probes.
According to another embodiment of the invention, the inertial platform is connected to the running gear of the undercarriage probe or with its structure and with a means of processing signals to determine faults in the geometry of the track.
According to another embodiment, the position of the said platform with respect to the chassis is measured each time by the sensors with which it is provided, which means that this platform can be connected to an independent device on the chassis.
The said platform may be equipped in all three measuring planes with accelerometers and gyroscopes and means of processing signals to determine all very specific faults in the track.
According to another embodiment, the inertial platform may either be achieved using mechanical means, or opto-electronic means. These inertial to platforms have been used for some time in aviation to determine the position of an aircraft and also in other circumstances in applications which are predominantly but not solely aeronautical.
It is obvious that other measuring bases may be used to take the bearings of the track, since the aim of this invention is to provide a vehicle through which any possible deformation of the chassis may be measured when travelling on the railway track, so that the results of measuring the actual position of the track are not hampered by errors, and also secondly to offer a measuring base having the advantages of an inertial platform.